1. Field of the Invention
This invention relates generally to electrosurgery and, more specifically, to a bipolar electrosurgical device for use in precision surgery. The device is an inexpensive, disposable, yet fully effective, probe body capable of performing focused treatment of the target tissue.
2. Description of the Prior Art
The use of heat for the cauterization of bleeding wounds dates to ancient times. In the present century, the use of radio frequency (RF) electrical current traveling through a portion of the body has been widely used to stop bleeding. Cauterization of tissue arises by virtue of its resistivity to RF energy. In the cauterization of blood, the proteins in it are heated to a temperature at which the proteins congeal in a manner similar to the process involved in the cooking of egg white. RF energy is preferred because its frequency is above that which could otherwise cause neuro-muscular stimulation. Several modes of RF cauterization of tissue are employed, such as monopolar or bipolar coagulation.
In monopolar coagulation, an active electrode of small dimensions such as of the order of one to two millimeters is applied to the bleeding site and the current path is completed through the body to a distanced electrical return plate in contact with a large surface area of the body such as the buttocks. One technique in which the monopolar mode may be employed involves fulguration which is the use of a spark or arc from the active electrode to the tissue. In bipolar coagulation, the two active electrodes are closely spaced and are of the order of fractions of millimeters or larger so that the current path is confined to a local region of the tissue.
Another technique for stopping bleeding involves the delivery of thermal energy, such as from a resistively heated probe as described in an article entitled "The Heater Probe: A New Endoscopic Method For Stopping Massive Gastrointestinal Bleeding" by R. L. Protell appearing in Vol. 74, No. 2, Part 1, pages 257-262 of Gastroentology, 1978.
A comparison of various coagulating techniques appears at pages 362-366 of an article entitled "Endoscope Thermal Treatment of Upper G.I. Bleeding", by J. H. Johnson, Endoscopy Review, July, 1986, pp. 12-26. Thus, it is well known that tissue proteins coagulate at temperatures of 50.degree.-100.degree. C.
The coagulation of bleeding vessels such as in the case of bleeding ulcers in gastrointestinal parts of the body generally requires use of a long endoscope from the distal end of which the bleeding area first must be identified and subsequently treated with an instrument passed through a channel provided in the endoscope. Locating the bleeding site is not easy since often the tissue wall being investigated may be moving, debris in the form of particles is likely to be present and interfere with vision and the blood flow itself tends to obscure the bleeding sources. These sources can be very small, of the order of less than a millimeter across, with many present in a particular area and each to be coagulated.
The endoscope, or the device inserted through it, therefore, is also provided with a wash channel through which a fluid such as a liquid or gas can be supplied to flush away the debris and permit visual scrutiny of the tissue area to be treated. In the above identified Endoscope Laser Treatment article, a flow of gas which is coaxial with the laser fiber is used to clear tissue. In a known electrosurgical device of the bipolar type, a pair of conductors are embedded in the wall of a catheter whose central bore is used to supply gas or liquid to the tissue area to be treated. The conductors project in the form of spaced-apart loops from a distal end of the catheter.
When a tissue area is to be treated, each tiny source of blood is subjected to heat treatment. This means the clearing of tissue with a wash of fluid, followed by the application of heat, again clearing the area and applying heat and so on until all of the bleeding areas have been coagulated. In such treatment, the repeated applications should be made with facility in an accurate manner with a minimum of undesirable side effects such as the sticking of the coagulating device to tissue areas.
The laser technique has the advantage of not requiring physical contact, and thus avoiding such sticking problems, but because of the variable way in which different tissue conditions permit absorption of the laser energy, precise control during tissue treatment is difficult. The monopolar electrosurgical device tends to injure tissue not intended to be treated and even cause damage in the target area itself such as by excessively deep effects in the target area. Hence, bipolar electrosurgical treatment of tissue has been proposed and used to improve safety inasmuch as the electric current is confined to the small area between electrodes. Over the years, numerous bipolar devices have been devised.
For example, starting with an early 1875 U.S. Pat. No. 164,184 to Kidder, a bipolar electrosurgical device is proposed wherein a pair of conductors are spirally wound onto a rubber probe body in which the conductors are embedded. The conductors are shown terminated at a distal hemispherically shaped end of the probe body. A thermally heated knife is described and shown in the U.S. Pat. No. 1,366,756 to R. H. Wappler who employed a pair of half-round cross-sectionally shaped conductor rods twisted about an insulator to connect to a heater-knife. In 1934, Kimble proposed a bipolar electrosurgical device in U.S. Pat. No. 1,983,669 wherein a pair of conductors are shown twisted around a common insulator and project from a retainer body in a manner useful for side-wise or head-on application to a tissue area.
The U.S. Pat. No. 4,011,872 to Komiya proposes an electrosurgical device wherein, for example, as shown in FIGS. 5, 9 and 11, one conductor is connected to a high frequency energy source and is formed of three or four electrodes. The electrodes individually extend from a distal end with spacings between electrodes being variable to accommodate or grasp differently sized tissue areas. In the U.S. Pat. No. 3,987,795 to Morrison, an electrosurgical device is described to operate in a mode which is intermediate the mono and bipolar modes of electrosurgery. This is achieved by mounting on one body, made of ceramic or glass, an active electrode and a return electrode whose surface area is made significantly larger than that of the active electrode. Various probe configurations are illustrated in the drawings.
Although these prior art electrosurgical devices are useful, they often do not provide satisfactory operation for a number of reasons. For instance, as previously noted, it is important that the probe body with which a cauterizing high frequency current is supplied can be repeatedly and precisely made to impinge upon the tiny blood vessel openings in the tissue area being treated independent of the orientation of the probe. This requires that as the probe is manually controlled at the proximal end of an endoscope, proper electrical contact is achieved to coagulate a blood vessel or other tissue target area whether the probe body is applied head-on, obliquely or side-wise to the tissue area.
Use of electrode configurations, as shown or described in the above prior art, thus frequently is unsatisfactory because of the larger number of probe applications needed to treat a tissue target or achieve coagulation of a bleeding tissue area.
The commonly assigned U.S. Patent No. 4,532,924 to Auth et al discloses an improved electrosurgical device according to which a more consistent and accurate tissue treatment is obtained with a multiple bipolar probe body on which at least one pair of conductors is distributed in a predetermined manner. As described with respect to one embodiment, the probe body is sized so that it can be passed through a channel of an endoscope from its proximal end. The probe body is provided with electrodes which are branched to form a plurality of electrode strips. The electrodes of different conductors are selectively sized and generally uniformly distributed in spaced apart pairs, over the distal end and side of the peripheral surface of the probe body. The ratio of the width of the electrodes to the spacing between them is so selected as to provide, with a predetermined minimum number of spaced apart pairs of electrodes, omnidirectional multiple bipolar treatment of tissue when the probe body is operatively projected from the distal end of the endoscope.
The use of one or more pairs of electrodes of which may be branched to form a plurality of electrode strips assures at least bipolar or multiple bipolar tissue contact when the probe body is applied while the probe body is small enough to electrically coagulate the individual blood vessels from the distal end of an endoscope. A particularly effective probe body in accordance with the invention disclosed in commonly assigned U.S. Pat. No. 4,764,331 issued Aug. 23, 1988, entitled "Focused Treatment Probe" employs at least six electrode strips, from one or more pairs of electrodes, constituting the equivalent of six bipolar coagulating devices, around the peripheral surface of the endoscopically passable probe body. With such an electrosurgical device, two or more of the electrode strips make tissue contact independent of the orientation of the probe body for effective treatment of tissue. That invention is particularly applicable to the treatment of cancerous tumors such as in the esophageal, rectal or anal areas, and may also be used for the treatment of hemorrhoids, although it is applicable to treat tissue in a wide range of other body locations as well, both internal and external. In all of these applications the area to be treated is usually only a portion of the wall of the duct and thus the instrument minimizes harm to healthy tissue adjacent to the cancerous area by appropriately locating the electrodes on the probe body.